PMID:11731805
| Citation |
Bandarian, V, Pattridge, KA, Lennon, BW, Huddler, DP, Matthews, RG and Ludwig, ML (2002) Domain alternation switches B(12)-dependent methionine synthase to the activation conformation. Nat. Struct. Biol. 9:53-6 |
|---|---|
| Abstract |
B(12)-dependent methionine synthase (MetH) from Escherichia coli is a large modular protein that uses bound cobalamin as an intermediate methyl carrier. Major domain rearrangements have been postulated to explain how cobalamin reacts with three different substrates: homocysteine, methyltetrahydrofolate and S-adenosylmethionine (AdoMet). Here we describe the 3.0 A structure of a 65 kDa C-terminal fragment of MetH that spans the cobalamin- and AdoMet-binding domains, arranged in a conformation suitable for the methyl transfer from AdoMet to cobalamin that occurs during activation. In the conversion to the activation conformation, a helical domain that capped the cofactor moves 26 A and rotates by 63 degrees, allowing formation of a new interface between cobalamin and the AdoMet-binding (activation) domain. Interactions with the MetH activation domain drive the cobalamin away from its binding domain in a way that requires dissociation of the axial cobalt ligand and, thereby, provide a mechanism for control of the distribution of enzyme conformations. |
| Links |
PubMed Online version:10.1038/nsb738 |
| Keywords |
5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase/chemistry; 5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase/metabolism; Binding Sites; Crystallography, X-Ray; Enzyme Activation; Escherichia coli/enzymology; Models, Molecular; Movement; Peptide Fragments/chemistry; Peptide Fragments/metabolism; Protein Structure, Secondary; Protein Structure, Tertiary; S-Adenosylmethionine/metabolism; Vitamin B 12/metabolism |
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